Cell Division

Mitosis

The essential biological process of cell division, fundamental for growth, repair, and reproduction in all eukaryotic cells.

Mitosis

It serves as the basis for the development of multicellular organisms from a single cell and is critical for the continuous renewal of tissues, with approximately 100 billion cells being replaced daily in an adult human body.

Nuclear division

Mitosis is the process of nuclear division specifically occurring in eukaryotic cells.

Accurate distribution

This process ensures the precise and accurate distribution of chromosomes to new cells.

Identical daughter cells

It produces two genetically identical daughter cells from a single parent cell.

Distinct from meiosis

Mitosis is distinct from meiosis, which is involved in sexual reproduction and produces genetically unique cells.

Interphase

It is the longest phase of the cell cycle, accounting for over 90% of a cell’s life.

Interphase

In this critical period, the cell grows, carries out its normal functions, and meticulously prepares for the upcoming division by replicating its DNA

G1 phase

The cell grows in size and performs its regular metabolic activities.

S phase

DNA synthesis occurs, where the cell meticulously replicates its entire genome. 6.4 billion base pairs.

G2 phase

The cell continues to grow, synthesize proteins, and replicates organelles, making final preparations for mitosis.

Chromosome condensation

Chromosomes condense, becoming visible under a microscope. In humans, the 46 chromosomes become tightly packed.

Sister chromatids form

Each replicated chromosome consists of two identical sister chromatids, joined at the centromere, forming an -shape.

Nuclear envelope breakdown

The nuclear envelope, which encloses the nucleus, breaks down, and the nucleolus disappears.

Spindle formation

Spindle fibers, made of microtubules, begin to form from the centrosomes, which move to opposite poles of the cell

Metaphase

It is a crucial stage where all the condensed chromosomes precisely align themselves along the metaphase plate, an imaginary plane equidistant from the two spindle poles, located at the cell’s equator.

Spindle fiber attachment

Spindle fibers, extending from the centrosomes, meticulously attach to the centromeres of each sister chromatid

Critical checkpoint

Ensures that every chromosome is properly aligned and attached to the spindle fibers. This precise alignment is essential for accurate chromosome segregation in the next phase.

Aneuploidy risk

Any misalignment or failure to attach correctly can lead to non-disjunction, resulting in an abnormal number of chromosomes in the daughter cells, a condition knows as aneuploidy.

Anaphase

Sister chromatid separation

Chromatid separation

The cohesin proteins holding sister chromatids together are cleaved, allowing them to separate. Each chromatid is now considered an individual chromosome.

Movement to poles

The newly independent chromosomes are rapidly pulled by the shortening spindle fibers towards opposite poles of the cell.

Anaphase

Typically the shortest phase of mitosis, often lasting only a few minutes, highlighting the speed and efficiency of this critical separation

Chromosomes decondense

Chromosomes arrive at the poles of the cell and begin to decondense, returning to their less compact state

Nuclear envelopes reform

New nuclear envelope form around each set of chromosomes at the poles, creating two distinct nuclei within the single cell

Spindle disappearance

The spindle fibers, which facilitated chromosome movement, disassemble and disappear

Cytokinesis

The cytoplasm divides, forming a cleavage furrow in animal cells, pinching the cell into two.

Two identical daughter cells

The culmination of mitosis and cytokinesis is the formation of two distinct, genetically identical daughter cells, ready to begin their own cell cycles

Growth

Mitosis enables the growth of organisms from a single-celled zygote into a complex multicellular entity, like a human with approximately 37 trillion cells.

Repair

Mitosis is crucial for repairing damaged tissues, such as wound healing, where new cells are needed to replace injured ones

Replacement

Mitosis ensures the continuous turnover of old or dead cells, replacing them with new, healthy ones

Asexual reproduction

For single-celled organism like yeast, mitosis is the primary method of asexual reproduction, allowing them to create genetically identical offspring

Non-disjunction

This refers to the uneven distribution of chromosomes during cell division, leading to daughter cells with an abnormal number of chromosomes, such as Trisomy 21

Uncontrolled division

Errors in mitotic checkpoints or mutations in genes that regulate the cell cycle can lead to uncontrolled cell proliferation

Abnormal proliferation/ cell death

Mitotic errors can also result in cells that are unable to divide properly, leading to abnormal cell growth, or conversely, triggering programmed cell death